Inducement and prevention of secondary branching and abnormal bolting of garlic

Every year, a certain proportion of garlic appears secondary branching and abnormal bolting during the bolting period, which seriously affects the yield and quality of garlic bolting. In recent years, we have carried out investigation and research, and explored the agricultural measures to effectively control the occurrence of secondary branches and abnormal bolting of garlic, which has played a very significant role in improving the economic benefits of garlic farmers.

1 the harm caused by secondary branches and strange bolts of garlic

The secondary branch of garlic, also known as secondary growth and bifurcation, is called "horsetail garlic". Generally, there are two phenomena: one is to differentiate from the outer leaf sheath to form a compound garlic, and the other is to differentiate into a loose garlic from the inner leaf sheath. After the production of secondary branches, the main bolts of garlic became shorter and thinner, and even could not be drawn out, and the yield of garlic bolts decreased by 70%, which basically lost its commerciality. In severe years, the incidence of secondary branching of "Ershuizao" reached 90%, and the incidence of "March yellow" reached 45%. In 2005, there were 33 hectares of "Ershuizao" garlic in Yuhua Town, Dafeng City, which caused the loss of garlic stalk harvest due to the serious occurrence of secondary branching, which caused huge losses to garlic farmers.

The deformity of garlic bolts is that garlic bolts become thicker and shorter, bolting is not smooth, forming garlic bolts swollen and curved, and the loss of commercial nature, the masses call it "strange bolts". According to multi-point surveys for many years, Ershui early strange bolts occur every year, with an incidence of 5% to 15% in general years and 30% to 40% in severe years. The incidence of strange bolting of yellow garlic in March is relatively low, from 1% to 2% in a general year and 5% to 10% in a high year.

2 the main reasons for the formation of secondary branches

The reasons for the formation of secondary growth of garlic are complicated, in addition to variety factors, differences in climate and cultivation factors are the main causes.

2.1 Climatic factors

Although garlic has strong tolerance to low temperature, it is sensitive to temperature, especially the vernalization stage of garlic requires lower temperature and time. Generally, the plants after sowing can pass the vernalization stage after sowing at 0: 10 ℃, after 1-2 months. Through the experiment, the secondary branching rate of Ershui early garlic was 53.54% when it was treated at 5: 10 ℃ for 30 days before sowing, while the secondary branching rate of untreated garlic was only 8.51%, which was 6.29 times that of the control, which indicated that the garlic treated with low temperature had passed the vernalization stage.

2.2 cultivation factors

Excessive growth of ① before sowing in early winter is easy to produce secondary branching. In recent years, garlic farmers blindly pursue the early listing of garlic bolts. At the same time, because of the large area, for staggering agricultural work, early sowing leads to early seedling development and increased bifurcation. According to the investigation on the sowing date of March yellow garlic in 2004, the secondary branching rate of fields sown at the end of August and early September was 60%, while that of March yellow garlic sown in mid-late October was only 5%. This shows that postponing the sowing date can significantly reduce the probability of secondary branching of garlic.

The influence of ② sowing density and branch number on garlic sowing density too sparse will lead to the lateral growth of garlic in the early stage, the pseudostem thickens, the scale disc is large, and it is easy to produce lateral buds to develop into bifurcations, especially Ershui early. According to the investigation in 2003, a farmer in Yuhua Town of Dafeng City planted 4669 square meters of Ershui early garlic, planted 37500 plants with equal row spacing of 667 square meters, and applied phosphate fertilizer 100kg, cotton cake 75kg and urea 30kg. 75% of the plants were decentralized before overwintering, and finally the plants were ploughed and replanted because most of the garlic bolts lost their commercial character.

Improper fertilization of ③ will also cause the second bifurcation of garlic to increase the tolerance of garlic to fertilizer and the demand for fertilizer. However, if there is too much nitrogen fertilizer in the application of base fertilizer, in the case of early sowing, a growth peak will be formed before winter, and a large number of branches will be produced after winter; for example, if spring fertilizer is applied too early, there is too much nitrogen in the plant, and the lack of bolting fertilizer in the later stage will also promote the increase of branches and reduce the yield of the main bolting.

3The main reasons for the formation of strange bolts.

The formation of strange bolts of garlic is mainly caused by garlic virus disease. The development of the new leaves of the diseased plant was blocked, the plant type became shorter, the leaves and pseudostems were deformed and twisted, and the garlic bolts could not be pulled out, resulting in a swollen neck. The source of the virus is caused by the transmission of peach aphids and the asexual reproduction of garlic.

4 measures to prevent secondary branching and reduce strange bolting

4.1 sowing at the right time and reasonable close planting

In order to ensure that garlic can grow well before winter and grow normally after winter, garlic is generally required to grow to 5-6 leaves, pseudo-stem thick 0.5~0.6cm and seedling height 20cm before winter. According to this requirement, in normal years, open field cultivation Ershui should sow as early as late September, plastic film cultivation should sow in mid-October, March yellow open field cultivation should sow in the first and middle of October, and plastic film cultivation should sow from late October to early November. At this time, seedlings emerge about 15 days after sowing, which is conducive to the formation of strong seedlings before overwintering.

When sowing, the row spacing of 6cm × 15cm is about 60 000 plants / 667m2, and the sowing amount is generally about 200kg/667 m2. The density of Ershui is 70000 ~ 80,000 plants / 667 square meters, which can not only improve the yield and quality of garlic bolts and heads, but also effectively prevent the occurrence of secondary bifurcation of garlic.

4.2 cultivation with plastic film

Garlic is sensitive to temperature, Rain Water and light in the early and middle stages of growth. In recent years, with warm winter and cold spring, the air temperature changes greatly and the dry and wet alternating frequently, which directly affects the stable growth of garlic and the weakening of disease resistance, resulting in different degrees of disease and the incidence of bifurcation and strange bolting between years. According to the observation in the past ten years, the disease occurs seriously when the temperature is high in winter and spring and the humidity in the field is high, and the secondary bifurcation and strange bolting of garlic are serious. If there is low temperature and less rain in winter and spring, the disease will be mild and the secondary bifurcation will be less. Since plastic film cultivation was popularized in 1998, the bifurcation and strange bolting of garlic have an obvious downward trend through multi-point investigation. Especially in the year of great occurrence of secondary branching in 2004, the incidence of secondary branching under plastic film cultivation decreased significantly.

The reason why plastic film mulching can control the occurrence of bifurcation and strange bolting is that plastic film can increase temperature and heat preservation, improve the ecological environment of garlic root, and effectively prolong the time of vernalization stage of garlic.

4.3 Scientific operation of fertilizer and water

Garlic is mainly based on base fertilizer, supplemented by topdressing, mainly organic fertilizer, supplemented by available fertilizer, increasing the application of phosphorus and potassium fertilizer, controlling the amount of nitrogen fertilizer, and actively popularizing soil testing formula fertilization technology. In the application method, sufficient base fertilizer, wax fertilizer and bolting fertilizer should be applied to prevent garlic from flourishing before winter, so that garlic can survive the winter at the right age, grow steadily in the middle stage, bolting strong seedlings and prevent premature senescence in the later stage. The garlic stalk has the advantages of uniform thickness, high yield and good quality, enhanced stress resistance and mild disease. General field base fertilizer applied organic fertilizer 1000kg, phosphate fertilizer 40~50kg, urea 15~20kg or 150kg high quality garlic formula fertilizer every 667m2. The mature human and animal manure 1000kg or urea 15kg was applied with wax fertilizer and urea 15~20kg was applied with bolting fertilizer every 667m2 to promote garlic bolting.

4.4 Disease control

Garlic disease mainly occurs in the middle and later stage, and the occurrence of the disease will also aggravate the secondary branching and strange bolting of garlic. The main diseases of garlic are leaf blight, leaf blight and leaf spot. Alternately spray 70% methyl thiophanate 800x solution, 25% mancozeb 400x solution, 75% chlorothalonil 500x solution, 50% prohydantoin 1000 fold solution or 50% Sukeling 500x solution at the initial stage of the disease. Seed soaking and foliar spraying with 100-fold solution of 83 increasing resistance agent can effectively reduce the occurrence of strange bolting.